For multi-view imaging systems, FIG. 11 is a diagram showing an example of camera arrangement having a straight-line alignment, FIG. 12 is a diagram showing another example of camera arrangement having a planar arrangement, FIG. 13 is a diagram showing another example of camera arrangement having an arc arrangement, and FIG. 14 is a diagram showing another example of camera arrangement having a spherical arrangement.
The multi-view imaging systems for imaging a scene in different directions have been developed. In the multi-view imaging systems, the camera arrangement has various forms such as a one-dimensional arrangement on a straight line as shown in FIG. 11, a two-dimensional arrangement on a plane as shown in FIG. 12, an arc arrangement as shown in FIG. 13, or a spherical arrangement as shown in FIG. 14. Using such multi-view imaging systems makes it possible to archive video scenes in many directions.
In addition, there is a technique called “image synthesis” for generating image information at a virtual camera position (at which imaging is not performed) by using camera images obtained by multi-view imaging.
In the image synthesis, it is assumed that a camera parameter which indicates the spatial direction in which the original video image was obtained is known. The image synthesis can be performed by various methods.
For example, there is a method of performing synthesis by estimating depth information. First, disparity information is obtained by searching corresponding points between original video images, and depth information of the relevant scene is estimated based on the disparity information. Then, depth information at the virtual camera position is estimated, and corresponding image information is generated using image information of the original cameras (see Non-Patent Document 1).
In another example of the methods, no estimation of depth information is performed, but image information at the virtual camera position is directly generated using disparity information of original images (see Non-Patent Document 2).
In another example, a plurality of camera images are used for estimating a three-dimensional model information of an object which is present in the relevant scene, and an image of the model projected from the virtual camera position is generated (see Non-Patent Document 3).
In the above-described imaging systems, cameras having the same bit depth (i.e., degradation) are generally used, however, those having different bit depths may be used. It is possible to reduce the amount of obtained image information by using a combination of a camera having a high bit depth and a camera having a low bit depth.
Tone mapping is a method for obtaining an image having a high bit depth based on an image having a low bit depth (see Non-Patent Document 4). This is a method for transforming quantized values into a signal having a higher dynamic range by means of mapping.    Non-Patent Document 1: Keita Takahashi and Takeshi Naemura, “Layered Light-Field Rendering with Focus Measurement”, EURASIP Signal Processing: Image Communication, vol. 21, no. 6, pp. 519-530 (2006.7).    Non-Patent Document 2: M. Droese, T. Fujii, and M. Tanimoto, “Ray-Space Interpolation Constraining Smooth Disparities Based On Loopy Belief Propagation”, Proc. of IWSSIP2004, pp. 247-250, Poznan, Poland, September 2004.    Non-Patent Document 3: Takashi Matsuyama, Takeshi Takai, Xiaojunn Wu, and Shohei Nobuhara, “Generation, Editing, and Visualization of 3D Video”, Proceedings of The Virtual Reality Society of Japan, Vol. 7, No. 4, pp. 521-532, 2002.12.    Non-Patent Document 4: E. Reinhard, M. Stark, P. Shirley, and J. Ferwerda, “Photographic Tone Reproduction for Digital Images”, presented at SIGGRAPH, 2002.